1. Field of the Invention
The present invention relates to an optical device module which is provided with a solid-state image sensor for photographing an object and is built in a digital camera, mobile phone with camera, digital video camera or the like, and relates to an optical path fixing device built in such an optical device module for fixing an optical path to the solid-state image sensor, further more, relates to a method for manufacturing such optical device module as described above.
2. Description of Related Art
A solid-state image sensor for use in a digital camera or a mobile phone with camera is used for capturing image of an object to be photographed and provided as an optical device module integrally assembled together with a lens, an infrared ray (IR) shield material, and an signal processing device for processing electric signal converted from image captured by the solid-state image sensor. Such a digital camera or a mobile phone with camera in which the optical device module is built in has now been demanded for downsizing. In response to or in advance of the demand for downsizing, the optical device module has been decreased in the overall size.
In the optical device module, an optical center of an effective pixel area of the solid-state image sensor needs to coincide with an optical center of a lens, and a plane made by the pixel area needs to intersect an optical axis of the lens at a right angle. In a case where positioning accuracy of the lens with respect to the solid-state image sensor is low, problems occur such that the solid-state image sensor may be out of focus or a dim image of the object to be captured is generated. For the reason, in a conventional optical device module, by previously incorporating an adjusting mechanism for focusing, focusing is carried out after assembling the conventional optical device module. However, as the adjusting mechanism which is used only in the assembling process is previously incorporated in the conventional optical device module, it will interrupt the downsizing of the optical device module. For compensation, some prior art schemes described below have been developed.
In Japanese Patent Application Laid-Open No. 2003-110946, proposed is a solid-state image sensor module package having a configuration in which a solid-state image sensor is adhered on a circuit board, a housing for holding an IR filter is adhered on the circuit board so as to enclose the solid-state image sensor, and a holder for holding a lens is fixed to the housing. In this prior art, since the holder and the housing is fixed by pressing, the assembling process is simplified.
Also in Japanese Patent Application Laid-Open No. 2004-297282, proposed is a camera module having a configuration in which a holding material for holding a lens and an optical filter is adhered by an adhesive to a package on which an image sensor is mounted. In this prior art, adhering is carried out with use of the adhesive consists of two different adhesives: a volatile curable adhesive which is cured as it volatilizes and an ultraviolet curable adhesive which is cured when exposed to ultraviolet ray, thus allowing the position of the lens to be adjusted after temporal adhering. When the position of the lens has been adjusted, the adhesive is exposed to ultraviolet ray for curing. In this prior art, since the position of the lens can be adjusted after the temporal adhering, it can be improved in the accuracy of positioning the lens.
Further, in Japanese Patent Application Laid-Open No. 2004-301938, proposed is an optical device module having a configuration in which an signal processing device for processing signals outputted from a solid-state image sensor is adhered to a wiring board, the solid-state image sensor is adhered on the signal processing device, a transparent cover is adhered to the surface of the solid-state image sensor, and a lens holding material for holding a lens is adhered to the transparent cover. In this prior art, since the lens holding material is adhered to the transparent cover, and the transparent cover is adhered on the surface of the solid-state image sensor, the accuracy of positioning the lens relative to the solid-state image sensor can be improved.
However, the image sensor module package disclosed in Japanese Patent Application Laid-Open No. 2003-110946 adopts the configuration in which the holder for holding the lens is fixed to the housing adhered on the circuit board. Accordingly, any manufacturing error which is derived from the circuit board or the housing may interrupt the relative positional relationship of the lens to the solid-state image sensor.
The camera module disclosed in Japanese Patent Application Laid-Open No. 2004-297282 adopts the configuration in which the holding material for holding the lens is adhered to the package. When the package is deflected or distorted at its surface, which serves as a reference plane for adhering, by the effect of manufacturing error, it may interrupt the accuracy of positioning the lens relative to the image sensor.
The optical device module disclosed in Japanese Patent Application Laid-Open No. 2004-301938 adopts the configuration in which the lens holding material is adhered to the transparent cover, and the transparent cover is adhered to the solid-state image sensor. Since the adhering between the solid-state image sensor and the transparent cover is carried out by a sheet form adhesive, the transparent cover can be adhered to the solid-state image sensor with high accuracy, thus improving the positional accuracy of the lens relative to the transparent cover. In this prior art, however, since the signal processing device, the solid-state image sensor and the transparent cover are placed upon the substrate while the lens holding material is adhered to the transparent cover, the solid-state image sensor, the signal processing device and the like may be injured by any impact urged on the lens holding material.
Moreover, each of the prior arts, the lens holding material for holding the lens is adhered by the adhesive to the transparent cover, the substrate or the like. It is however difficult to apply a uniform thickness of the adhesive at coating. Since, at the time of adhering the lens holding material to the transparent cover, adhering portion is parallel to the upper surface of the transparent cover, that is, the radial direction of the lens, there is a fear that the optical path is intersected by overflowing excessive adhesive when adhesive is excessively coated.